The present invention generally relates to a mounting method, and more particularly, to a die-bonding method for pellets and the like.
Referring to FIGS. 3A and 3B, a conventional die-bonding method for pellets will be described hereinafter.
In the first place, as shown in FIG. 3A, a needle 12 having a through-bore 10 for evacuation or vacuum formation provided therein is brought into contact with an upper portion or bump portion of a pellet 8 (a diode with a bump at its upper portion in this example) located at a first position as it is accommodated within a recess 4 of a pellet holding jig 2, through evacuation via a through-bore 6 formed at the bottom portion of said recess 4, by lowering said needle 12 from an imaginary line position indicated by a two-dotted chain line to a position shown by a solid line in a direction of an arrow a, whereby the pellet 8 is attracted onto the forward end of the needle 12, in which state, said needle 12 is raised in a direction indicated by an arrow b. Subsequently, the needle 12 is horizontally moved in a direction indicated by an arrow c, i.e. towards a paste 18 applied at a predetermined portion of a frame 16 disposed on a base 14 at a second position, and then, as shown in FIG. 3B, the needle 12 is lowered in a direction of an arrow d from the imaginary line position shown by the two-dotted chain line to the solid line position, thereby to bring the pellet 8 attracted onto the forward end of the needle 12, into contact with the paste 18. Thereafter, the pellet 8 is caused to adhere to the paste 18 by releasing the through-bore 10 of the needle 12 from the evacuation, and thus, die-bonding of the pellet 8 onto the frame 16 is completed.
In the known die-bonding practice as described so far, however, there has been such a problem that, since it is required to subject the through-bore 10 of the needle 12 to the evacuation or vacuum formation, and also, to effect a timing control for the evacuation, as the number of pellets to be die-bonded increases, vacuum forming systems corresponding in number to such an increase becomes necessary, and as a result, the arrangement on the whole is extremely complicated, with a consequent rise in cost.
Another problem inherent in the conventional die-bonding method is such that, when the needle 12 in a state where no pellet 8 is attracted by vacuum to its forward end is lowered with respect to the second paste 18 in the direction of the arrow d in FIG. 3B and the forward end thereof contacts the paste 18, there is a possibility that the through-bore 10 of the needle 12 is undesirably closed or clogged by the paste 18, and detecting control system for detecting whether or not any pellet 8 is attracted onto the forward end of the needle 12, etc., is also required. From such a point, not only complication and high cost of the entire arrangement are involved, but, the possibility of clogging the forward end-of the needle 12 by such contact will remarkably reduce reliability of the die-bonding arrangement.